In the prior art it is known to make patterned multi-colored sheet gold by the traditional diffusion bonding processes such as Japanese mokume-gane technique, but these techniques are inadequate for mass production. This process involves heating layers of different colored sheet metals under pressure until bonding occurs. The resulting billet is a multi-colored sandwich that can be manipulated into a variety of patterns. In order to expose the colors contained within, the billet must be further worked by forging, bending or twisting. Engraving, filing, grinding, chiseling, machining, and other material removal means have also been used to create colored patterns.
This process, however, has proven to be ineffective for large scale production. The difficulty in pouring consistently successful ingots of the zincless alloys necessary in a heat-soaking process such as mokume-gane has proven unduly expensive and time consuming. Also, the quantity of the material produced as such as limited to the size and pressure capacities of many available bonding furnaces.
Subsequent to the production of the billets, further inconvenience is encountered when manipulating the sheet material to form patterns. The amount of machining required is complicated, expensive and time consuming. In addition, the machining of the sheet metal causes burrs at grooved intersections which burrs must be removed before subsequent rolling. In final preparation, the grooves in the machined metal must be rolled out to expose the routed pattern to the outer surface. This rolling causes excessive elongation and distortion of the design. Finally, the machined grooves can create undesirable stresses within the sheet material when the metal is rolled.